PMSM sensorless control based on second-order sliding mode observer

A kind of second-order sliding mode observer is proposed to estimate the rotor position and speed of PMSM (Permanent Magnet Synchronous Motor), which combines the linear sliding mode with the hybrid non-singular terminal sliding mode to avoid the phase lag caused by the low-pass filter in conventional sliding mode observer and to improve the precision of rotor position and speed estimation. The sliding mode control law is designed to restrain the inherent chattering and to guarantee the stability of observer. The tracking algorithm with phase-lock function is employed to demodulate rotor position and speed from the observed back electromotive force. Simulative and experimental results demonstrate the validity of the proposed observer.